Variability of Ice and Ocean Fluxes

in the Arctic/Sub-Arctic Domain

Michael Karcher, R. Gerdes, F. Kauker, C. Köberle, U. Schauer

Alfred Wegener Institute for Polar and Marine Research

SEARCH Open Science MeetingOctober 27, 2003Seattle, Washington, USA

NAOSIM

Freshwatercontent

NAOSIM model setup

MOM 2 based coupled to sea-ice model

0.25o resolution on rotated spherical grid

30 levels

Open boundary at 50oN

Initial condition: EWG + Levitus et al. (1994)

Spin up: 20 years climatology with daily variability based on ECMWF

NCEP forcing 1948-2002

Rüdiger Gerdes, Frank Kauker, Cornelia Köberle, Jennifer Brauch, Jörg Hurka, Kerstin Fieg

Temperature and Salinity Observations in the West Spitzbergen Current (Fram Strait Branch)

Propagation of temperature anomalies in the Arctic Ocean

Velocity cm/s

Tpot°C

Gerdes et al., GRL 2003

1990s

1960s

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Arctic warming events

Temperature at the level of the temperature maximum

cold anomaly(→ NABOS)

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See Karcher et al., JGR 2003

Propagation of temperature anomalies:

Warmest events in 60s and 90s

90s event outstanding in intensity and spatial extent

(large volume flow and reduced heat loss)

Important role of the Barents Sea

NAOSIM

Barents Sea salinity

inflow

outflow

? ?

NAOSIM model results(Karcher et al., in prep)

Ice balance

Barents Sea ice im- and export

large net export

large net import

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Maximum densities in deep Barents Sea outflow

Observed low

Observed high

Observations: Schauer et al, 2002

Observed medium values

Now. Zem. Polynia Icegrowth

Barents Sea dense water outflow:

mean densities:

sea-ice balance variabilityseems

as influential as AW inflow variability

peak densities:

local ice formation/salt release

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Arctic halocline 1968 vs. 1998

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Reduction of Arctic Ocean Freshwater pool

Arctic Ocean

Nordic Sea

-14000 km3

+ 4000 km3

Change in trend or again

decadal fluctuation?

Freshwater Inventory (total watercolumn)NAOSIM

SSS Ano-malie

1994 1995

1996 1997

Fram Strait 0-90m

Denmark Strait 0-90m

Arctic Subarctic low-saline surface outflow

Significant alterations

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Fram Strait

Denmark Strait

Iceland-FaroeFaroe-Scotland

Canadian Arch.

Liquid Freshwater fluxes Nordic Sea (ref. 34.8)NAOSIM

Advective liquid balance

Surface fluxes

Residual freshwater

Nordic Sea Freshwater budgets (NAOSIM NCEP hindcast)

Phases of net freshwater surplus

Advective sea-ice balance

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Nordic Sea freshwater budget:

variability of sea-ice balance at least as important as

variability of liquid balance

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Deep Denmark Strait Salinity

Black: NAOSIM model results

Obs

Blue: Observations [Dickson et al., 2002]shifted -0.035

[Dickson et al., 2002]

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DSOW signals:

Temperature:

Decadal signals

Salinity:

Decadal signals plus freshening trend -weaker in model than in observations

... due to restoring?

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What‘s up next:

• Freshwater storage and release dynamics (e.g. ASOF-FAST)

• Model intercomparison / Atlantic Water dynamics (AOMIP)

• Comparison of model results with new analyses of modern and historic data (…T, S, Tracer)

• and as always: model improvement, new forcing data sets, …

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NAOSIM

0-90 m

90-280 m

280-970 m

Black: Fram Strait

Blue: Denmark Strait

Temperature signalspassing along the East Greenland Coast